Genes are segments of DNA that carry hereditary information determining traits. The double helix model of DNA was discovered in 1953 by Watson and Crick based on Rosalind Franklin's research using X-ray diffraction that showed DNA's spiral staircase structure. DNA contains the genetic material passed down from parents and is composed of nucleic acids including nucleotides of purines and pyrimidines. RNA also contains nucleic acids but has different types that serve various functions in protein synthesis and cell processes. Mutations in DNA can be beneficial or detrimental and cause changes in genetic sequences.